1) I see the T1 and T2 architecture supplements are available ( UST1-UASuppl-current-draft-P-EXT.pdf and UST2-UASuppl-current-draft-HP-EXT.pdf ). They are incomplete (at least SPU and MAU specifications are missed), but they are here.

I couldn't find T4 architecture supplement. Is it available ?

2) I noted that sun4u architecture (from Sun UltraSPARC's III, IV and up to modern Fujitsu SPARC64 VII+) has 64-bit virtual address space (there is no hole in).

Unfortunately, in sun4v T1 and T2 chips VA space was degraded to 48-bit (the only value of "mmu-#va-bits" md property I have seen).